capabilities carried over execve()

[Eric Buddington]

I am attempting to write an init replacement that is capability-smart.
Though I'm pleased that prctl() lets me keep capabilities across a
setreuid(), maintaining caps over execve() seems impossible to do right.

I currently see a few options:
	- use the CLOEXEC-pipe hack that execcap uses (parent notices
	  when pipe closes then rushes to set caps on child before
	  child notices they're gone). This looks like a race to me.
	- tweak linux/fs/exec.c (prepare_binprm) to pretend that all
	  files have cap_inheritable and cap_effective fully set.
	  This seems a more elegant solution, but requires a kernel
	  patch.
	- exec the child in a stopped state, mess with caps, then
	  send it SIGCONT. AFAIK, there is no way to do
	  execve_and_stop.

Is there a better solution available, or one in the works?
I think capabilites may be a key to achieving Pretty Good (tm) security
- but then again, so is running bind as non-root, and nobody even
bothers to do that...

-Eric